Heads up! A satellite is expected to fall to Earth sometime Sunday night or Monday morning, and scientists can't say yet where it will land. The satellite, known as GOCE, has been circling our planet since 2009, when it was launched by the European Space Agency (ESA) to map Earth's gravity. It weighs 2,425 pounds, and its altitude has been dropping since late October, after it ran out of fuel. GOCE is a bit bigger than a Volkswagen van, but it won't be crashing to Earth in one piece.

The science fiction movie "After Earth" marks a homecoming of sorts for star Will Smith, a Philadelphia native. A major portion of the Columbia Pictures movie, which opens Friday, was filmed at the new Sun Center Studios outside Philadelphia that is also not far from where director M. Night Shyamalan was raised. In "After Earth," Smith plays a general who returns to earth with his son -- played by Jaden Smith -- 1,000 years after humans have left. Although some key scenes of the film were shot in the redwoods of Northern California , as well as in Costa Rica and Utah, Sun Center Studios wasted no time touting its own ties to the movie -- and its Hollywood stars.

October 17, 2013 | By Sergei L. Loiko, This post has been corrected and updated. See below for details.

ST. PETERSBURG, Russia -- Ukrainian astronomers say an asteroid might collide with Earth in a couple of decades, a Russian news service reported Thursday. Space watchers from the observatory in the Crimean peninsula said they discovered an asteroid about 1,345 feet in diameter, which they call 2013 TV135, that is approaching Earth at a potentially dangerous trajectory, RIA Novosti said. The astronomers calculated the date of a potential collision as Aug. 26, 2032, the news service said, but they acknowledged the odds of an impact as 1 in 63,000.

On Thursday night, an asteroid about the size of a 14-story building will hurtle past Earth at the mind-bending speed of 7 miles per second. And one month ago, scientists didn't even know it existed. Asteroid 2012 QG42 was just discovered on Aug. 26 by astronomers at the Catalina Sky Survey in Arizona. It has been classified as a PHA (Potentially Hazardous Asteroid) by the Minor Planet Center based in Cambridge, Mass. That sounds kind of scary, but scientists say there's no need to worry -- at least not yet. The asteroid is not expected to get closer to Earth than 7.5 x the distance of the moon from Earth. (The moon's distance from Earth fluctuates, but it averages 230,600 miles)

Scientists studying Martian clouds have created them right here on Earth. Using a cloud chamber in Germany and rock from the Mojave Desert, their experiment shows that the Red Planet's ice clouds often need far more humidity to form than clouds on Earth. The findings, published in the Journal of Geophysical Research: Planets, show that Martian clouds form under very different conditions than many scientists once thought - which may help researchers to better understand the planet's water cycle.

Earthlings, get ready to say cheese! NASA's Cassini spacecraft will be taking your picture next month -- from 898 million miles away. If you happen to have your eyes closed or your hair is out of place, don't worry. All of planet Earth will fit into 1.5 pixels in the final image. Most of the frame will be filled by Saturn and its gigantic rings (though some of the edges will be cut off). Scientists at the Jet Propulsion Laboratory in La Canada Flintridge are taking the picture - actually, a mosaic of images - because they can. It just so happens that Cassini and the sun will be on opposite sides of Saturn, allowing the spacecraft to see the planet and its famous rings with unusual clarity.

Early Thursday morning, solar observers watched as a dark spot on the sun erupted with an enormous flash of light, causing the biggest solar flare of 2013. Solar flares themselves don't last long, but this one was powerful enough to cause a bubble of solar material called a CME (coronal mass ejection) to come bursting off the sun. Up to billions of tons of that solar material is now hurtling through space at the mind-bending speed of more than 600 miles per second, and it is heading directly toward Earth.

Looking for a sign that the Republican Party might have some leaders who can appeal to younger voters? Mitt Romney cited the Beach Boys, Garth Brooks and the Eagles among his favorite musicians, but Sen. Marco Rubio raised some eyebrows Monday with hat tips to N.W.A and Public Enemy. Rubio, 42, who has sparked early 2016 presidential hype with a headlining visit to Iowa over the weekend, spoke to GQ about a number of topics, but his opinions on music and the Earth's age overshadowed his perspective on President Obama and young Republicans.

Asteroid 4179 Toutatis will zip past Earth this week. At its closest approach Tuesday night and into Wednesday morning, it will come within 18 lunar distances of the planet. That's 18 times the distance from the Earth to the moon. That may not sound too close, but the asteroid's erratic orbit occasionally has it zipping by a little too close for comfort. That's why the asteroid has been designated "potentially hazardous. " In 2004 for example, the asteroid's orbit took it even closer to the Earth -- just about four lunar distances.

Poring over images of Saturn's icy moon Iapetus, planetary scientists have discovered massive landslides in which the falling ice travels much farther than should be possible given the coefficient of friction of the falling ice. In one spectacular case in the moon's Malun crater, ice broke off the wall of the 5-mile-deep crater and surged 22 miles across the crater floor -- an unusually long distance. Given that cold ice has a relatively high coefficient of friction, such long distances should not be possible unless there are forces at work that researchers don't yet know about, said planetary scientist William McKinnon of Washington University in St. Louis, who led the team studying the landslides.